(n.)South African word describing a dodgy character. Someone who steals, lies and generally is not to be trusted. A township gangster. Can also be used as a light insult to friends. Pronounce it as you read it, say the 'ts' part quickly, as an interrupted 's' sound.

Help! That tsotsi just stole my cell phone!
Don't mix with those tsotsi's, they're hijackers.
Slang - You are such a tsotsi for stealing my drink.